1. Field of the Invention
The present invention relates to the manufacture of shoes, especially sporting shoes and boots having high uppers, such as ice-skating boots, ski boots or football boots. It will be understood that the general term "shoe" as used in this specification and appended claims applies to all high-cut shoes including those known as "boots".
2. Description of the Prior Art
In order to provide greater strength and/or in order to ensure water-tightness of certain parts of a shoe, it has already been proposed to manufacture them by providing molded parts of plastic on elements which may be made of leather or any other suitable material and which serve as supports for the molded parts. A design solution of this type has already been proposed with a view to reducing production costs.
Thus French Pat. No. FR 1,353,780 describes a method of manufacture which consists in injecting plastic between the outsole and the insole of a shoe, the upper of the shoe having already been joined to the insole of said shoe in a previous operation. However, the injection of plastic is strictly limited to the sole and in no way involves the upper of the shoe. The same remark applies to the methods described in French Pat. Nos. FR 1,580,513 and 2,339,356.
In regard to French Pat. No. FR 2,420,312, this specification describes a shoe having an external shell of plastic overmolded on an inner slipper of leather. The outsole is molded at the same time on a stiffening reinforcement which constitutes the counter for the heel of the shoe as well as a thin intermediate sole. This shoe offers undoubted advantages in regard to stability of shape and water-tightness. A disadvantage, however, is that a shoe of this type is relatively heavy and has an unattractive appearance by reason of the conspicuous presence of the outer plastic shell.
In a completely different order of ideas, French Pat. No. FR 2,493,112 describes a method of manufacture of a slipper which is intended to be placed within a ski boot. In accordance with this method, the slipper is formed by injecting plastic foam between an inner sock of fabric and an outer sock constituted by a thin extensible film of polyurethane. The injection proposed in the cited patent takes place through an orifice provided in the top portion of the outer sock. The layer thus injected is uniform and of the same nature, both in the upper portion of the slipper and in the portion corresponding to the sole. This method therefore does not result in the formation of a true sole which is comparable with the sole of a shoe. Such a result is in any case not even contemplated by the method considered since it is concerned only with the manufacture of an internal slipper for the purpose of forming a virtual shock-absorbing and protective cushion around the user's foot.
In consequence, the different methods recalled in the foregoing are in no way applicable to the manufacture of a shoe of the high-upper type in which both the sole and the upper have to be reinforced, with the exception, however, of the method described in French Pat. No. FR 2,430,312. However, this method suffers from the major drawbacks mentioned earlier.
It is for the reasons given in the foregoing that the object of the present invention is to propose a method of manufacture which affords the advantages of overmolding of a layer of plastic but is not subject to any of the disadvantages attached to present-day shoes of this type. With this objective, the basic concept of the method in accordance with the present invention makes it possible to obtain a shoe having the appearance of a normal leather shoe in which any potential danger of detachment of the molded layer of plastic is completely removed.